The present invention relates to flame proofing compositions, and more particularly, it relates to phosphorus-containing flame proofing compositions for synthetic materials and to synthetic materials containing such flame proofing agents.
Some phosphorous flame proofing mixtures effective for flame proofing polymeric materials, and especially for flame proofing flexible or rigid polyurethane foams, have been described in U.S. Pat. No. 4,144,387. The mixtures described in this patent contain the 2-chloroethyl phosphonate of bis-(2-chloroethyl): ##STR3## and high-boiling polyphosphonates, including among others a dimer composition of the proposed structure: ##STR4##
Good results are obtained with these mixtures in accelerated thermal aging tests.
Nevertheless, the mixtures described in this patent have the drawback of crystallizing easily at ambient temperatures. Thus, a commercial product according to the aforesaid patent, made by Mobil Oil Corporation under the name "Antiblaze 78", contains about 65% by weight of the chloroethyl phosphonate of bis-(chloroethyl) and about 35% of high-boiling polyphosphonates obtained directly by thermal isomerization of tris-(2-chloroethyl) phosphite, as shown in the patent, and it contains about 12% by weight of phosphorus, this material having a crystallization temperature of about 23.degree. C. Some mixtures according to the foregoing patent, prepared in the laboratory or on a pilot scale, by direct isomerization of the tris-(2-chloroethyl) phosphite under various operating conditions of temperature and reaction volume, and containing quantities comprised between 60 and 85% of the chloroethyl phosphonate of bis-(chloroethyl) similarly show crystallization temperatures of from about 20.degree. to 30.degree. C. This ready crystallization at ambient temperatures constitutes a major drawback in the commercial use of such mixtures, due to the risk of solidification during their storage or use, with attendant fouling of pumps and piping.